1. Field of the Invention
The present invention relates to a hardness tester and to a method for a hardness test.
2. Description of Related Art
Conventionally, indentation-type hardness testing methods are well known, such as the Vickers hardness test and the Knoop hardness test, in which an indenter having a polygonal shape in a plane view is pressed against a surface of a sample, then a hardness value is measured from a length of a diagonal line in a resulting polygonal indentation in the sample surface. These methods are often used to evaluate mechanical characteristics of metallic materials. (See, e.g., Japanese Patent Laid-open Publication No. 2011-220790.)
The Vickers hardness test employs a quadrangular pyramid diamond indenter and indicates the hardness value by a relationship between an average value for the length of the two diagonal lines of the quadrangular pyramid indentation formed in the surface of the sample and a pressing load (test force) of the indenter on the sample. The Knoop hardness test employs a rhomboid pyramid diamond indenter and indicates the hardness value by a relationship between the length of the longer of the diagonal lines of the rhomboid pyramid indentation formed in the surface of the sample and the test force of the indenter on the sample.
Thus, in a Vickers hardness tester, when the test force is F and the average value for the length of the two diagonal lines of the indentation formed in the sample is d, a hardness value HV can be calculated using Formula 1.HV=0.1891 F/d2  [Formula 1]
However, in conventional hardness testers, the hardness value is measured based on the length of the diagonal lines of the indentation that remains after the indenter has been withdrawn from the sample. Therefore, the same hardness value may be measured even when samples have different elasticity, for example. The conventional hardness testers have thus been unable to distinguish the elasticity of a sample.